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Animal Nutrition AnSc 315 > Nutrient Digestion and Digestibility > Flashcards

Nutrient Digestion and Digestibility Flashcards

1
Q

what is nutrient digestibility

A
  • chemical analysis of feed provides information on nutrient composition
  • no information on digestibility in digestive tract (extent of digestion important
  • indication of bioavailability of nutrients (nutrients that is available for metabolism)
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2
Q

what is digestibility

A
  • the proportion of a feed that is not excreted in the feces and, therefore is assumed to have been absorbed
  • major determinant of nutritional value of feeds

digestible matter + undigestible matter = 100%

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3
Q

what is the concept of digestibility

A

high digestibility = high nutritional retention = high performance (positive for economics, less so for environment (manuer = nitrogen and phosphorus)
low digestibility = low nutrient rentention = poor performance

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4
Q

what are the methods of measure for feed digestibility

A
  • in vivo
  • in sotu
  • in vitro
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5
Q

what is in vivo

A
  • total fecal collection
  • indicator method
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6
Q

what is in situ

A
  • nylon bag
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7
Q

what is in vitro

A
  • tilley and terry method
  • gas prodcution
  • enzymes
  • regression using chemical analysis
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8
Q

what are step in vivo measurement of digestibility

A
  • test feed or diet given to animal in known amounts for several days - 4-14 adaption period (4-7 days to measure feed intake then collect feces)
  • 4-6 animals fed test or diet, digestibility differs; statistical analysis requires replication (consistent feed intake; time of feeding)
  • can use males of females
  • housed in metabolism crates or stalls, measure fecal output
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9
Q

why do you need an adaption period for feed

A
  • allow time for old feed to be totally excreted (so only test feed is in the diet)
  • might take animals GI a bit of time to adapt to the new feed - microorganisms
  • feed intake might go down = environmental adaptation to new feed
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10
Q

what are metabolism crates

A
  • sheep and pigs- adaptation periods
  • fecal collection - fecal bags or tray behind animal
  • urine - delivered by funnel into collection Jar below
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11
Q

how do you use digestibility for total fecal collection

A
  • determine DM % and nutrient content of test feed ( CP crude fat NDF ADF)
  • feed animal in metabolic crate, measure FI
  • collect total fecal output
  • determine DM % and nutrient content in feces
  • determine total DW or nutrient intake and total DM or nutrient output in feces
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12
Q

what is the difference between apparent and true digestibility

A
  • most measurements of digestibility are apparent nutrient digestibility
  • enzymes + sloughed-off epithelial cells + microbial cells in feces = endogenous losses
  • when we dont account for endogenous loss = apparent
  • when we do account for endogenous loss = true protein ( true should always be higher, because in apparent you over estimate protein)
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13
Q

what are indirect measurement of digestibility

A
  • some feed ingredients cannot be fed as sole feed ( 100% grain to a ruminant (rumen acidosis) or 100% fat to any animal)
  • measure digestibility indirectly using two digestibility trials
  • first, determine digestibility of a basal diet which can be fed at the 100% level (the only feed the animal is getting)
  • then combine the basal with the test ingredient and measure the digestibility of the basal diet and the test ingredient in combination
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14
Q

what is step 1 in indirect measurement of digestibility

A
  • determine digestibility of the basal diet
  • 60% digestibility of alfalfa
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15
Q

what is step 2 in indirect measurement of digestibility

A
  • determine the digestibility of 50/50 alfalfa/grain (5kg each on DM basis)
  • fecal output = 2.5 kg
  • partition the feces source
  • 5 kg of alfala = 2 kg of feces (calculation)
  • 10kg of feed = 2.5 feces by test
  • 5 kg of grain = 0.5 kg feces by difference
  • ## digestibility of grain
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16
Q

what are problems with total collection

A
  • need accurate estimate of feed intake (feed wastage, animals on pasture)
  • must collect all fecal output ( volume of material can be large =, tedious and labour-intesive)
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17
Q

how do you measure digestibility with indicator method

A
  • mix an indigestible indicator into the feed at a low and known level (usually 0.5%) (with adataptation period
  • feed to an animal (no need to measure intake)
  • collect a grab sample of feces (no need to collect all)
  • measure concentration of indicator in feces
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18
Q

what are the properties of ideal indicator or marker

A
  • cannot be digested or absorbed from GI
  • inert, no toxic metals or metabolic effects
  • intimately associated with material that it is to mark (the diet )
  • uniformly excreted in feces (grab samples)
  • stable
  • inexpensive
  • readily available
  • easily detected, easy to measure
19
Q

what is an example of an internal digestibility marker

A
  • indigestible NDF
  • lignin (good for browse)
  • acid insoluble ash ( silicates)
20
Q

what is an example of an external marker of digestibility

A
  • chromic oxide (Cr2O3) - chemically added
  • titanium oxide or ytterbium - more expensive/ more difficult
21
Q

what is an in vitro techniques and in situ technique for watching digestibiltiy

A
  • stimulate rumen fermentation and small intestinal (gastric digestion) under controlled conditions
  • test tube
22
Q

what is tilley and terry

A

artificial rumen

23
Q

what is a nylon bag

A

have the feed placed in a nylon bag and place it in the GI
- 5cm x 15cm 50um filled with 2-5g ground feed sample
- pore size is important ( test feed in bag and tie tighly
- slowly digestible
- incubate in rumen for predetermined lengths of time 0-48 hours
0 accounts for original feed, making sure none is lost
wash bags, dry measure residue weight) CP NDF ADF

24
Q

what is the tilley and terry method

A
  • rumen fluid obtained from fistulated animals to provide source of rumen micro-organisms
  • digest feed (0.5g) with rumen liquor (same as rumen fluid) in system where CO2 is bubbled into tube to maintain anaerobic conditions for 48h at 39c
  • buffers so ph incubation doesnt go down to much
  • a second digestion is conducted using pepsin (50ml of 0.2% solution) for further 48h 39c
  • the undigested residue is weighed and nutrient digestibility estimated
  • incubate blank with ruminal fluid + buffer (not adding a feed to the blank flask, can get feed out of rumen)
  • can process large number of samples, quickly (rumen fluid is divided into many test tubes)
  • yields comparable data to in vivo
  • diet of donor animal, inoculum processing, length of incubation, sample processing ect. can insluence results
  • must grind original sample
  • must be consistent
25
Q

what is mobile nylon bag technique

A
  • nylon bag technique useful for determining feed digestibility in ruminant
26
Q

what issue happened with swine researchers

A
  • the fed bags were chewed and let feed escape
  • inserted bags into stomach, but got trapped in stomach bags could not pass plyloric sphincter
27
Q

what happened swine researchers positively

A
  • mimic digestion in the stomach by incubating bags with pepsin and Hal; then insert bags into the duodenum
  • you have to sit there and wait for feces, collect and look for bags to avoid continous microbial breakdown and put it in water
28
Q

what feed factors affect digestibility

A
  • level of dietary fibre
  • composition of fibre (when fibre goes up digestibility goes down)
  • stage of maturity of plant
  • processing of feed
  • anti-nutritional factors
  • feed additives
29
Q

how does fibre effect digestibility

A
  • as plants mature - the fibre content goes up
  • digestibility of the plant goes down
  • (less enzyme penetration of the cell wall - especially is lignin is high)
30
Q

what are the effects of composition of fibre on digestibility

A
  • fibre = cell wall content = cellulose + hemicellulose + lignin
  • cellulose and hemicellulose can be partially digested
  • lignin is indigestible
  • fibre with high lignin content is less digestible
31
Q

what are the effects of processing on digestibility

A
  • grinding and devilling
  • improves feed digestibility (particle zise reduction, removes barrier to enzyme penetraction
  • processing effects greater with pooer quality feeds (grinding has greastest inpact with high fibre feeds)
32
Q

effects of grinding in ruminants

A
  • can improve digestibility
  • excessive grinding of forages can be detrimental (reduces salvia secretion, reduces rumination and decreases the ratio of acetate to propionate)
  • greater rates of passage through rumen can reduce digestibility
33
Q

effects of anti-nutritional factors on digestibility

A
  • some feeds can contain anti-nutritional factors
    (trypsin inhibator - raw soybeans, tannins faba beans, glucosinolates (rapeseed)
  • can significantly reduce nutrient digestibility
34
Q

effects of feed additives on digestibility

A
  • use of exogenous enzymes to improve the nutrition value of feeds (major focus of research)
  • phytases, B glucanases and xylanases
35
Q

what is phytate

A
  • 60-75% of p in cereal grains bound as phytate
  • phytate utilization in monogastric low (no phytase expression)
  • dietary inclusion of inorganic P to meet the animals requirement
  • also P excretion
36
Q

what is phytase

A
  • improves P digestibility in cereal grains
  • benefits ( can reduce inorganic P) ( reduce feeding costs; environment benefit )
37
Q

what is the enviropig

A
  • genetically - engineered pig
  • can use phytate P
  • No P supplementation - 65% less manure P; save on feeding costs
38
Q

what are animal factors that can affect digestibility

A
  • species of animal
  • age of animal
  • level of feeding
  • health status
39
Q

effect of animal species on digestibility

A
  • digestibility coefficients for feeds variable (type of animal fed, conditions under which the feed is fed)
  • ruminants vs non ruminants (fibre digestibility
40
Q

effect of age of animal on digestibility

A
  • the ability to digest fibre sources increases with age (develops with rumen)
  • larger fore-stomachs or hind-gut
  • ## expression of digestive enzymes also increases
41
Q

effects of level of intake on digestibility

A
  • at high levels of intake, rate of passage increases (reduces digestibility)
  • fibre digestion in ruminants
  • faster rate of passage reduces digestibility = less opportunity to digest
  • reduces ability of fermentation
42
Q

how does cold temperature effect digestibility

A
  • cold temperature reduces digestibility because of the higher increase of DM eaten
43
Q

how do seasons effect nutrient digestibility

A
  • greater water consumption in the summer increases passage rate
  • making intake go up and decreases digestibility
  • consuming more water, because of water lost due to panting and sweating

Animal Nutrition AnSc 315 (12 decks)

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